<template>
  <div class="spec-preview">
    <img :src="imgObj.imgUrl" />
    <div class="event" @mousemove="handler"></div>
    <div class="big">
      <img :src="imgObj.imgUrl"  ref="big"/>
    </div>

    <!-- 绿色蒙版 -->
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  name: "Zoom",
  props: ["skuImageList"],
  data() {
    return {
      currentIndex: 0,
    };
  },
  methods: {
    handler(event) {
      // 获取dom元素
      let mask = this.$refs.mask;
      let big = this.$refs.big;
      // 计算位移量
      let left = event.offsetX - mask.offsetWidth / 2;
      let top = event.offsetY - mask.offsetHeight / 2;
      // 约束范围
      if (left <= 0) left = 0;
      if (left >= mask.offsetWidth) left = mask.offsetWidth;
      if (top <= 0) top = 0;
      if (top >= mask.offsetHeight) top = mask.offsetHeight;
      //  修改蒙版的left/top属性
      mask.style.left = left + "px";
      mask.style.top = top + "px";
      // 修改大图big的属性
      big.style.left = -2 * left + "px";
      big.style.top = -2 * top + "px";
    },
  },
  computed: {
    imgObj() {
      return this.skuImageList[this.currentIndex] || {};
    },
  },
  mounted() {
    // 全局时间总线，获取兄弟组件imageList传过来的值
    this.$bus.$on("getIndex", (index) => {
      // 修改当前响应式数据
      this.currentIndex = index;
    });
  },
};
</script>

<style lang="css">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;
}
.spec-preview img {
  width: 100%;
  height: 100%;
}
.spec-preview .event {
  width: 100%;
  height: 100%;
  position: absolute;
  top: 0;
  left: 0;
  z-index: 998;
}
.spec-preview .mask {
  width: 50%;
  height: 50%;
  background-color: rgba(0, 255, 0, 0.3);
  position: absolute;
  left: 0;
  top: 0;
  display: none;
}
.spec-preview .big {
  width: 100%;
  height: 100%;
  position: absolute;
  top: -1px;
  left: 100%;
  border: 1px solid #aaa;
  overflow: hidden;
  z-index: 998;
  display: none;
  background: white;
}
.spec-preview .big img {
  width: 200%;
  max-width: 200%;
  height: 200%;
  position: absolute;
  left: 0;
  top: 0;
}
.spec-preview .event:hover ~ .mask,
.spec-preview .event:hover ~ .big {
  display: block;
}
</style>